Display device and planar light source device

ABSTRACT

The present invention relates to a technique which makes a backlight used in a liquid crystal display device thin and light-weight. The present invention provides a liquid crystal display device which includes a display panel and a backlight arranged behind the display panel, wherein the backlight includes a film-like light guide member, a film-like light semi-transmissive member adhered to a first surface of the light guide member which faces the display panel in an opposed manner, a film-like reflective member adhered to a back surface of the light guide member opposite to the first surface, and a spot light source arranged at a position of the light guide member at which light is incident on the light guide member from the first surface or the back surface. A refractive index of the light semi-transmissive member is set smaller than a refractive index of the light guide member.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation application of U.S.application Ser. No. 13/137,326 filed Aug. 5, 2011, which is aDivisional application of U.S. application Ser. No. 12/923,481 filed onSep. 23, 2010, which is a Divisional application of U.S. applicationSer. No. 11/634,262 filed on Dec. 6, 2006. Priority is claimed from U.S.application Ser. No. 13/137,326 filed on Aug. 5, 2011, which claimspriority from U.S. application Ser. No. 12/923,481 filed on Sep. 23,2010, which claims priority from U.S. application Ser. No. 11/634,262filed on Dec. 6, 2006, which claims priority from Japanese application2005-352167 filed on Dec. 6, 2005, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device and a planar lightsource device, and more particularly to a technique which is effectivelyapplicable to a planar light source device which radiates lightpropagated through a light guide plate and a display device which usesthe planar light source device.

2. Description of the Related Arts

Conventionally, as a display of a mobile phone or a notebook-type PC(Personal Computer) or the like, a liquid crystal display device (aliquid crystal display unit) having a liquid crystal display panel isused.

The liquid crystal display device is roughly classified into atransmissive-type liquid crystal display device which displays an image(a video) by arranging a backlight (a light source) behind the liquidcrystal display panel and radiating light from the light source to theliquid crystal display panel and allowing the light to pass through theliquid crystal display panel, and a reflective-type liquid crystaldisplay device which displays an image (a video) by reflecting lightfrom outside a display device on a liquid crystal display panel.

Further, the backlight of the transmissive-type liquid crystal displaydevice is roughly classified into, for example, a direct-type backlightwhich arranges a light source such as a fluorescent tube in a regionwhich is overlapped to a display region of a liquid crystal displaypanel, and an edge-light-type (also referred to as a side-light-type)backlight which arranges a light guide plate in a region which isoverlapped to a display region of a liquid crystal display panel andarranges a light source on an end portion of the light guide plate.

The edge-light-type backlight is a backlight which radiates light to theliquid crystal display panel by propagating light from the light sourcewhich is arranged on the end portion of the light guide plate in theinside of the light guide plate, directing the light in the directiontoward the liquid crystal display panel by a reflective portion formedon a back surface of the light guide plate and by diffusing the lightusing a diffusion plate. The edge-light-type backlight can reduce athickness thereof compared to a thickness of the direct-type backlight.Accordingly, the liquid crystal display device having theedge-light-type backlight has been often used in a display of a mobilephone or a notebook-type PC.

Further, with respect to the edge-light-type backlight, to uniformlyradiate light to the display region of the liquid crystal display panel,there has been known a backlight which uses a combination of a lightguide plate to which a shape which efficiently reflects the propagatinglight (for example, grooves) is applied and a reflective sheet (forexample, see Japanese Patent Laid-open No. 11599/2005 (patent document1)).

Further, with respect to the edge-light-type backlight, to achieve thereduction of thickness of the backlight, for example, there has beenknown a backlight which is constituted of a light guide body layer (alight guide plate), a reflection layer (a reflective portion) and adiffusion layer (a diffusion plate) as the integral structure, whereineach layer is formed of a thin film sheet (for example, see JapanesePatent Laid-open Hei08-152526 (patent document 2)).

SUMMARY OF THE INVENTION

However, for example, in the backlight described in the above-mentionedpatent document 1, the reflection grooves or the like are formed in thelight guide plate and hence, a gap is defined between the reflectivesheets and light infiltrates into the gap. Further, due to the formationof the grooves, there exists light which reflects or refracts at anangle which does not contribute to the front face brightness.Accordingly, there has been a drawback that loss of light is increased.Further, in general, the light guide plate is often formed by injectionmolding and hence, there has been a drawback that it is difficult toform the light guide plate into a shape as designed from a viewpoint offorming accuracy.

Further, for example, the backlight described in the above-mentionedpatent document 2 makes use of the generation of a total reflection onan interface between the sheets by combining thin film sheets havingdifferent refractive indexes. However, no consideration has been takenby the patent document 2 with respect to an incident angle of light whenthe light is incident on the light guide body layer from the lightsource. Accordingly, for example, the light which is incident on thelight guide plate at a small incident angle which does not generate thetotal reflection becomes dominant thus giving rise to a drawback thatlight cannot be effectively radiated into the inside of a display regionof the liquid crystal display panel.

Further, in the liquid crystal display device (the liquid crystaldisplay unit) which is used in a mobile phone or the like, recently, toachieve the reduction of weight of the liquid crystal display device,for example, a spot light source such as an LED (Light Emitting Diode)is used as the light source of the backlight. However, the backlightdescribed in the patent document 2 premises the use of a linear lightsource such as a fluorescent tube as the light source. Accordingly, forexample, when the spot light source such as the LED is used, there hasbeen a drawback that it is difficult to make the brightness distributionof the light which is radiated into the inside of the display region ofthe liquid crystal display panel.

Accordingly, it is an object of the present invention to provide atechnique which can achieve the reduction of thickness and the reductionof weight of a backlight used in a liquid crystal display device, forexample.

It is another object of the present invention to provide a techniquewhich can achieve the reduction of thickness, the reduction of weight ofa backlight used in a liquid crystal display device, and the increase ofbrightness of the liquid crystal display device, for example.

The above-mentioned and other objects and novel features of the presentinvention will become apparent from the description of thisspecification and attached drawings.

To explain the summary of typical inventions among the inventionsdisclosed in this specification, they are as follows.

(1) In a display device which includes a display panel and a backlightwhich is arranged behind the display panel, the backlight includes afilm-like light guide member, a film-like light semi-transmissive memberwhich is adhered to a first surface of the light guide member whichfaces the display panel in an opposed manner, a film-like reflectivemember which is adhered to a back surface of the light guide memberopposite to the first surface, and a spot light source which is arrangedat a position of the light guide member at which light is incident onthe light guide member from the first surface or the back surface,wherein a refractive index of the light semi-transmissive member is setsmaller than a refractive index of the light guide member.

(2) In a display device which includes a display panel and a backlightwhich is arranged behind the display panel, the display panel adheres apolarizer on a surface thereof which faces the backlight in an opposedmanner and a back surface thereof opposite to the surface, and thebacklight includes a film-like light guide member, a film-likepolarization reflective member which is adhered to a first surface ofthe light guide member which faces the display panel in an opposedmanner, a film-like reflective member which is adhered to a back surfaceof the light guide member opposite to the first surface, and a spotlight source which is arranged at a position of the light guide memberat which light is incident on the light guide member from the firstsurface or the back surface, wherein a transmission axis of thepolarization reflective member is directed in the same direction as atransmission axis of the polarizer which is adhered to the surface ofthe display panel which faces the backlight in an opposed manner.

(3) In the display device having the above-mentioned means (1) or (2),the backlight includes a reflector which is arranged in the directionthat the spot light source radiates the light in the film surfacedirection of the light guide member and allows the light radiated fromthe spot light source to be incident on the light guide member byreflecting the light.

(4) In the display device having the above-mentioned means (1) or (2),the light semi-transmissive member or the polarization reflective memberchanges a ratio of transmissivity and reflectance of light whichpropagates in the light guide member corresponding to a distance from aposition at which the light of the light guide member is incident.

(5) In the display device having the above-mentioned means (1) or (2), aplurality of through holes are formed in a plurality of portions of thelight semi-transmissive member or the polarization reflective member,and the distribution density of the through holes is changedcorresponding to a distance from a position at which the light of thelight guide member is incident.

(6) In the display device having the above-mentioned means (1) or (2),the reflective member changes reflectance thereof corresponding to adistance from a position at which the light of the light guide member isincident.

(7) In the display device having the above-mentioned means (1) or (2),the reflective member has an irregular reflection pattern formed of aconcave shape or a convex shape at a plurality of portions of a surfaceof the reflective member which is brought into close contact with thelight guide member, and the distribution density of the irregularreflection pattern is changed corresponding to a distance from aposition at which the light of the light guide member is incident.

(8) In a planar light source device having a light source and afilm-like light guide member, the light source includes a film-likeincident-light adjusting member which is arranged in the direction thatlight is radiated in the direction perpendicular to a film surface ofthe light guide member and changes the incident direction of light tothe light guide member to the propagation direction of light of thelight guide member between a region of the light guide member whichallows light to be incident thereon and a surface of the light sourcefrom which light is radiated, and the incident-light adjusting memberhas one, two or more projections on a surface side thereof which facesthe light guide member in an opposed manner, and distal end surfaces ofthe projections are brought into close contact with the light guidemember.

(9) In the planar light source device having the above-mentioned means(8), a light radiation surface of the light guide member has a radiationlight adjusting member which adjusts a radiation angle of the light fromthe light radiation surface.

(10) In the planar light source device having the above-mentioned means(8) or (9), the light guide member includes a reflective member on abacksurface thereof opposite to a surface thereof on which theincident-light adjusting member is arranged and in a region thereofwhich is overlapped to the incident-light adjusting member.

(11) In any one of the planar light source devices having theabove-mentioned means (8) to (10), the projections of the incident-lightadjusting member are columnar projections each of which has a curvedbottom surface.

(12) In a display device which includes a display panel and a backlightwhich is arranged behind the display panel, the backlight is formed ofthe planar light source device included in any one of the planar lightsource devices having the above-mentioned means (8) to (11).

The display device of the present invention adopts the constitution inwhich the portion which propagates the light of the backlight isintegrally configured such that, as shown in the above-mentioned means(1), the film-like light guide member is sandwiched between thefilm-like light semi-transmissive member and the film-like reflectivemember. Here, each member is integrally formed by adhering film-likeformed members having a thickness of 0.25 mm or less to each other, forexample. Due to such a constitution, the light guide plate can be madethin and light-weighted. Further, by adopting the integral constitutionformed of a film-like light guide member, a semi-transmissive member anda reflective member, light which is incident on the light guide memberpropagates through the light guide member while repeating the reflectionbetween the semi-transmissive member and the reflective member with highefficiency. Accordingly, loss of the light which propagates through thelight guide member is decreased thus increasing the brightness of thelight radiated to the display region of the display panel.

Further, in the display device of the present invention, theconstitution of the portion which propagates the light of the backlightmay adopt a film-like polarization reflective member in place of thesemi-transmissive member as in the case of the above-mentioned means(2).

Here, by adopting the above-mentioned constitution of the means (3), theloss of light can be reduced and hence, the brightness of light which isradiated to the display region of the display panel can be increased.Here, it is preferable that the above-mentioned reflector has areflective surface having a convex shape in the direction toward thespot light source, for example.

Further, by constituting the light semi-transmissive member or thepolarization reflective member as in the case of the above-mentionedmeans (4), it is possible to make the in-plane brightness of the lightradiated to the display region of the display panel uniform. Here, inplace of changing the ratio between the transmissivity and thereflectance of the light semi-transmissive member or the polarizationreflective member as in the case of the above-mentioned means (4), aplurality of through holes may be formed in the light semi-transmissivemember or the polarization reflective member by changing thedistribution density of the through holes as in the case of theabove-mentioned means (5).

Further, in place of changing the ratio between the transmissivity andthe reflectance of the light semi-transmissive member or thepolarization reflective member as in the case of the above-mentionedmeans (4), the reflectance of the reflective member may be changed as inthe case of the above-mentioned means (6). Here, in place of changingthe reflectance of the reflective member as in the case of theabove-mentioned means (6), a plurality of irregular reflection patternsmay be provided to a surface of the reflective member which is laminatedto the light guide member while changing the distribution density of theirregular reflection patterns as in the case of the above-mentionedmeans (7).

Further, when the light radiated from the spot light source is directedtoward the film surface of the light guide member as in the case of theabove-mentioned means (3), even when the light is reflected on thereflector, there may be a case that among the light which is incident onthe light guide member, the light whose incident angle does not exceed acritical angle becomes dominant. With respect to the light which isincident with the angle which does not exceed the critical angle andpropagates through the light guide member, there is no possibility thatsuch a light is totally reflected on an interface with the lightsemi-transmissive member or the polarization reflective member or aninterface with the reflective member. Accordingly, the light leaks tothe outside of the light guide member on each interface, and the lightdoes not propagate through the inside of the light guide member.

To overcome such a drawback, for example, as in the case of theabove-mentioned means (8), it is desirable to use the planar lightsource device which is arranged to radiate the light in the directionperpendicular to the film surface of the light guide member as the spotlight source. Here, the above-mentioned incident light adjusting membermay be arranged between the spot light source and the light guidemember. Due to such a constitution, the light of the spot light sourcewhich is radiated in the direction perpendicular to the film surface ofthe light guide member is allowed to be incident on the light guidemember while converting the incident angle thereof into an angle whichexceeds the critical angle in the inside of the light guide member usingthe incident light adjusting member. Accordingly, it is possible toallow the light of the spot light source to be effectively incident onthe light guide member thus acquiring the higher brightness uniformity.

Further, for example, as in the case of the above-mentioned means (9),the radiation light adjusting member which adjusts the radiation angleof the light from the radiation surface may be provided to the radiationsurface of light of the light guide member. The radiation lightadjusting member may be constituted in the same manner as theabove-mentioned incident light adjusting member, for example. Due tosuch a constitution, for example, even when the light guide member isnot sandwiched between the light semi-transmissive member and thereflective member, it is possible to radiate the light which is incidenton the light guide member in a planar shape while propagating the lightthrough the light guide member.

Further, by providing the reflective member as in the case of theabove-mentioned means (10), it is possible to allow the light which isradiated to the outside of light guide member to be reflected on theabove-mentioned reflective portion without making the incident angleexceed the critical angle using the incident light adjusting member thusallowing the light to be incident on the light guide member again.

Here, by adopting the constitution of the means (11), it is possible topropagate the light of the spot light source in a spreading manner inthe inside of the light guide member.

In this manner, with the provision of the planer light source devicehaving any one of the above-mentioned means (8) to means (11), it ispossible to allow the light of the spot light source to be effectivelyincident on and to propagate through the light guide member thusacquiring the high brightness uniformity. Further, by forming the lightguide member, the incident light adjusting member and the radiationlight adjusting member in a film shape, it is possible to realize thereduction of thickness and the reduction of the weight of the planarlight source device. Accordingly, as in the case of the above-mentionedmeans (12), with the use of the planar light source device having theany one of the above-mentioned means (8) to means (11) as the backlightof the display device, it is possible to realize the reduction ofthickness and the reduction of weight of the backlight and, at the sametime, the brightness uniformity of the display region can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the schematic constitution of adisplay device of an embodiment 1 according to the present invention;

FIG. 2 is an enlarged schematic view of an essential part of FIG. 1;

FIG. 3 is a schematic view for explaining a modification of theembodiment 1;

FIG. 4 is a schematic view showing the schematic constitution of abacklight of an embodiment 2 according to the present invention;

FIG. 5 is a cross-sectional view taken along a line A-A′ in FIG. 4;

FIG. 6 is a schematic view for explaining a modification of theembodiment 2;

FIG. 7 is a schematic view for explaining a variation of the embodiment2;

FIG. 8 is a schematic view showing the schematic constitution of abacklight of an embodiment 3 according to the present invention;

FIG. 9 is a cross-sectional view taken along a line B-B′ in FIG. 8;

FIG. 10 is a schematic view for explaining a modification of theembodiment 3;

FIG. 11 is a schematic view showing the schematic constitution of abacklight of an embodiment 4 according to the present invention;

FIG. 12 is a cross-sectional view taken along a line C-C′ in FIG. 11.

FIG. 13 is a cross-sectional view taken along a line D-D′ in FIG. 11;

FIG. 14 is a schematic view for explaining a modification of theembodiment 4;

FIG. 15 is a cross-sectional view taken along a line E-E′ in FIG. 14;

FIG. 16 is a cross-sectional view taken along a line F-F′ in FIG. 14;

FIG. 17 is a schematic view for explaining one of advantageous effectsof the backlight of the embodiment 4;

FIG. 18 is a schematic view showing a constitutional example of adisplay device which uses a conventional general backlight for comparingwith the backlight of the embodiment 4;

FIG. 19 is a schematic view showing the schematic constitution of abacklight of an embodiment 5 according to the present invention;

FIG. 20 is a cross-sectional view taken along a line G-G′ in FIG. 19;

FIG. 21 is a schematic view for explaining a mounting method of anincident-light adjusting member;

FIG. 22 is a schematic view for explaining the manner of operation ofthe backlight of the embodiment 5;

FIG. 23 is a schematic view showing one example of a method for adheringa spot light source and the incident-light adjusting member in theembodiment 5;

FIG. 24 is a cross-sectional view taken along a line H-H′ in FIG. 23;

FIG. 25 is a schematic view showing one example of the arrangement ofthe backlight and the display panel of the embodiment 5;

FIG. 26 is a schematic view showing another example of the arrangementof the backlight and the display panel of the embodiment 5;

FIG. 27 is a schematic view for explaining a first variation of theembodiment 5;

FIG. 28 is a schematic view for explaining a second variation of theembodiment 5;

FIG. 29 is a schematic view showing the schematic constitution of abacklight of an embodiment 6 according to the present invention; and

FIG. 30 is a cross-sectional view taken along a line J-J′ in FIG. 29.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is explained in detail in conjunctionwith embodiments by reference to drawings.

Here, with respect to the whole drawings for explaining the embodiments,parts having the same functions are given the same symbols and theirrepeated explanation is omitted.

(Embodiment 1)

FIG. 1 is a schematic view showing the schematic constitution of adisplay device of an embodiment 1 according to the present invention,while FIG. 2 is an enlarged schematic view showing an essential part ofFIG. 1.

In FIG. 1, numeral 1 indicates a display panel, numeral 201 indicates alight radiation portion, numeral 201 a indicates a light guide member (alight guide film), numeral 201 b indicates a light semi-transmissivemember (a light semi-transmissive film), numeral 201 c indicates areflective member (a reflective film), and numerals 3A, 3B indicatepolarizer films.

The display device of this embodiment 1 includes, for example, as shownin FIG. 1, the light radiation portion 201 of a backlight below thedisplay panel 1.

The display panel 1 may be any kind of display panel provided that thedisplay panel 1 allows light radiated from the light radiation portion201 of the backlight to pass therethrough and displays an image (avideo). As one example of the display panel 1, for example, a liquidcrystal display panel in which a liquid crystal material is sandwichedbetween a pair of substrates may be named. Further, in the display panel1, in general, as shown in FIG. 1, polarizer films 3A, 3B are adhered toa surface of the display panel 1 on which light radiated from thebacklight is incident and a surface of the display panel 1 from whichlight is radiated respectively.

The light radiation portion 201 of the backlight is, for example, asshown in FIG. 1 and FIG. 2, integrally configured such that the lightguide member 201 a is sandwiched between the light semi-transmissivemember 201 b and the reflective member 201 c. Here, the lightsemi-transmissive member 201 b is made of a material having a refractiveindex smaller than a refractive index of the light guide member 201 a.

Further, in the embodiment 1, the light guide member 201 a, the lightsemi-transmissive member 201 b and the reflective member 201 c arerespectively formed of a film-like member. Hereinafter, the light guidemember 201 a is referred to as a light guide film, the lightsemi-transmissive member 201 b is referred to as a lightsemi-transmissive film and the reflective member 201 c is referred to asa reflective film. Here, a thickness Ta of the light guide film 201 a isset to 0.25 mm or less, for example. Further, a thickness Tb of thelight semi-transmissive film 201 b and a thickness Tc of the reflectivefilm 201 c are respectively set to 0.05 mm or less, for example.

The light guide film 201 a is made of polycarbonate (PC) having arefractive index of 1.59, for example, while the light semi-transmissivefilm 201 b is made of fluororesin having a refractive index of 1.35, forexample. Here, the light semi-transmissive film 201 b may be also madeof polyethylene terephthalate (PET) having a refractive index of 1.57 oran acrylic UV curing resin having a refractive index of 1.49, forexample. Further, the reflective film 201 c is formed of a polyestermulti-layered film or a silver sheet which is prepared by sputteringsilver to a PET substrate.

Further, in the embodiment 1, the light guide member 201 a, the lightsemi-transmissive member 201 b and the reflective member 201 c areformed into the integral structure by adhering them to each other usingan optical adhesive agent having a refractive index which issubstantially equal to a refractive index of the light semi-transmissivemember 201 b, for example.

In the display device having such a constitution, for example, as shownin FIG. 1 and FIG. 2, light 4 is incident on the light radiation portion201 of the backlight from an end portion of a surface of the light guidefilm 201 a which faces the display, panel 1 in an opposed manner(hereinafter, referred to as a film surface). Then, the incident light 4is propagated in the inside of the light guide film while repeating thereflection between an interface with the light semi-transmissive film201 b and an interface with the reflective film 201 c. Here, on theinterface with the light semi-transmissive film 201 b, corresponding tothe relationship between a refractive index of the light guide film 201a and a refractive index of the light semi-transmissive film 201 b,light having a shallow angle, that is, light having a large incidentangle with respect to the light semi-transmissive film 201 b isreflected on the interface. On the other hand, light having a deepangle, that is, light having a small incident angle with respect to thelight semi-transmissive film 201 b is refracted on the interface and isradiated in the direction toward the display panel 1. The light which isreflected on the interface with the light semi-transmissive film 201 bis reflected on the interface with the reflective film 201 c and, again,is incident on the interface with the light semi-transmissive film 201b. By allowing the light which propagates through the light guide film201 a to repeat this operation, the light 4 incident on the light guidefilm 201 a is converted into a planar light and is radiated to thedisplay panel 1.

Here, although not shown in FIG. 1 and FIG. 2, a light source of thelight 4 which is incident on the light guide film 201 a may be arrangedat any position provided that the light 4 which is incident on the lightguide film 201 a propagates in the direction toward a region which isoverlapped to the display panel 1 from the light incident position.

In this manner, in the display device according to the embodiment 1, thethickness Ta of the light guide film 201 a is set to 0.25 mm or less andthe thickness Tb of the light semi-transmissive film 201 b and thethickness Tc of the reflective film 201 c are respectively set to 0.05mm or less. Accordingly, a total thickness of the thickness Ta of thelight guide film 201 a, the thickness Tb of the light semi-transmissivefilm 201 b and the thickness Tc of the reflective film 201 c can be, asa matter of course, set to a value larger than 0 and equal to or lessthan 0.35 mm. Further, by forming these films into the integralstructure, the light radiation portion 201 of the backlight can be madethin and light-weighted.

Further, by forming the light guide film 201 a, the lightsemi-transmissive film 201 b and the reflective film 201 c into theintegral structure, it is possible to propagate the light 4 which isincident on the light guide film 201 a by repeating the reflection ofthe light 4 with high efficiency on the interface with the lightsemi-transmissive film 201 b and the interface with the reflective film201 c. Accordingly, loss of light attributed to leaking of light onrespective interfaces, particularly, on the interface with thereflective film 201 c can be reduced and hence, it is possible toincrease the brightness of light which is radiated to the display panel1.

FIG. 3 is a schematic view for explaining a modification of theembodiment 1.

In the display device of the embodiment 1, by forming the light guidefilm 201 a, the light semi-transmissive film 201 b and the reflectivefilm 201 c into the integral structure, the light 4 which is incident onthe light guide film 201 a is propagated while repeating the reflectionof light with high efficiency between the interface with the lightsemi-transmissive film 201 b and the interface with the reflective film201 c. Here, the light semi-transmissive film 201 b is a member whichreflects or refracts the light (allows the light to pass through)corresponding to an incident angle of the light which is propagatedthrough the light guide film 201 a and is incident on the interface withthe light semi-transmissive film 201 b. That is, on the interfacebetween the light guide film 201 a and the light semi-transmissive film201 b, a portion of the light which is incident on the interface isreflected and is continuously propagated through the light guide film201 a and a remaining portion of the light is radiated to the displaypanel 1. Accordingly, the light radiation portion 201 of the backlightmay be formed of a film having a function equal to a function of thelight semi-transmissive film 201 b in place of the lightsemi-transmissive film 201 b. As a member which has the function equalto the function of the light semi-transmissive film 201 b, apolarization reflective film can be named, for example.

The polarization reflective film is, for example, a member whosepolarization surface allows only a component of the light which isdirected in a certain direction to pass through and reflects remainingcomponents of the light. Accordingly, with the use of the polarizationreflective film in place of the light semi-transmissive film 201 b, outof the light which propagates through the light guide film 201 a, onlythe component which agrees with a transmission axis (a polarizationaxis) of the polarization reflective film passes through thepolarization reflective film and is radiated to the display panel 1.Then, the remaining components are reflected and continuously propagatedthrough the light guide film 201 a. The light which is reflected on theinterface with the polarization reflective film 201 b is reflected onthe interface with the reflective film 201 c and, again, is incident onthe interface with the polarization reflective film 201 b. By allowingthe light which propagates through the light guide film 201 a to repeatthe operation, the light 4 which is incident on the light guide film 201a is converted into a planar light and is radiated to the display panel1.

Here, the light which is radiated to the display panel 1 from the lightguide film 201 a after passing through the polarization reflective filmis a light whose polarization surface agrees with the transmission axisof the polarization reflective film. Accordingly, in using thepolarization reflective film, for example, as shown in FIG. 3, when thepolarization reflective film 201 d is adhered to a surface of the lightguide film 201 a which faces the display panel 1 in an opposed manner, atransmission axis AX1 of the polarization reflective film 201 d isdirected in the same direction as a transmission axis AX2 of thepolarizer 3A which is adhered to a surface of the display panel 1 whichfaces the light radiation portion 201 in an opposed manner. Due to sucha constitution, the polarization surface of the light which is radiatedto the display panel 1 from the light guide film 201 a after passingthrough the polarization reflective film 201 d agrees with thetransmission axis AX2 of the polarizer 3A which is positioned in frontof the display panel 1 and hence, the light is allowed to pass throughthe polarizer 3A and to be incident on the display panel 1.

Further, by setting a thickness of the polarization reflective film 201d to 0.05 mm or less, for example, in the same manner as the lightsemi-transmissive film 201 b and by forming the polarization reflectivefilm 201 d, the light guide film 201 a and the reflective film 201 cinto the integral structure, the light radiation portion 201 of thebacklight can be made thin and light-weighted.

Here, in FIG. 3, the transmission axis AX1 of the polarizationreflective film 201 d is arranged parallel to a side of the light guidefilm 201 a on which the light is incident. However, provided that thedirection of the transmission axis AX1 agrees with the direction of thetransmission axis AX2 of the polarizer 3A which is adhered to thedisplay panel 1, the transmission axis AX1 may be directed in anydirection.

(Embodiment 2)

FIG. 4 is a schematic view showing the schematic constitution of abacklight of an embodiment 2 according to the present invention.Further, FIG. 5 is a cross-sectional view taken along a line A-A′ ofFIG. 4.

In the embodiment 2, on the premise of the constitution of theembodiment 1, a constitutional example of a light radiation portion 201which can obtain the in-plane uniformity of the brightness (the lightquantity) of light radiated on the display panel 1 is explained.

Here, the light radiation portion 201 of the backlight is, for example,as shown in FIG. 4 and FIG. 5, formed into the integral structure bysandwiching the light guide film 201 a between the lightsemi-transmissive film 201 b and the reflective film 201 c. A thicknessof the light guide film 201 a is set to 0.25 mm or less. Further,thicknesses of the light semi-transmissive film 201 b and the reflectivefilm 201 c are respectively set to 0.05 mm or less, for example.Further, the light guide film 201 a, the light semi-transmissive film201 b and the reflective film 201 c are respectively made of materialsexplained in conjunction with the embodiment 1. Further, the light guidefilm 201 a, the light semi-transmissive film 201 b and the reflectivefilm 201 c are formed into the integral structure by the methodexplained in conjunction with the embodiment 1.

Further, in this embodiment 2, a plurality of through holes (throughholes) TH is formed in a plurality of portions of the semi-transmissivefilm 201 b. The through holes TH are formed by etching the lightsemi-transmissive film 201 b, for example.

Further, the through holes TH are, for example, as shown in FIG. 4,formed in such a state that a plurality of rows in which a plurality ofthrough holes TH is arranged in parallel to a side of the light guidefilm 201 a on which a region L on which light is incident is formed isarranged in the propagation direction of the light. Here, it ispreferable to set intervals G1, G2, G3, G4, G5, G6, G7 between therespective through holes TH in a state that the remoter the intervalfrom the side of the light guide film 201 a on which light is incident,the smaller the interval becomes as shown in FIG. 4. Further, althoughthe number of rows of the through holes TH is eight in the example shownin FIG. 4, it is needless to say that the number of rows may be otherthan eight.

When these through holes TH are formed in the light semi-transmissivefilm 201 b, for example, as shown in FIG. 5, the light 4 which isincident on the light guide film 201 a from a certain position of thelight guide film 201 a propagates through the light guide film 201 afollowing a path indicated by a solid-line arrow. Here, the light whichis reflected on the reflective film 201 c and is incident on theinterface with the light semi-transmissive film 201 b is incident on aregion where the through holes TH are formed. The light which isincident on the region where the through holes TH are formed isrefracted and is radiated into inner spaces formed in the through holesTH. Then, the light is reflected or is refracted on side surfaces of thethrough holes TH and is radiated in the direction where the displaypanel 1 is arranged. That is, by forming the through holes TH, the lightis irregularly reflected on the side surfaces of the through holes THand is radiated in the direction where the display panel 1 is arranged.Accordingly, in comparison with the case of the embodiment 1, thein-plane uniformity of the brightness (light quantity) of the lightradiated to the display panel 1 is enhanced.

Further, the light which propagates through the light guide film 201 aexhibits a large light quantity in a region closer to the side on whichthe light is incident and the light quantity is gradually decreased asthe region is away from the side on which the light is incident.Accordingly, as shown in FIG. 4, by increasing the distribution densityof the through holes TH in the region remote from the side on which thelight is incident thus facilitating the irregular reflection of thelight, the in-plane uniformity of brightness (light quantity) of thelight which is radiated to the display panel 1 is further enhanced.

FIG. 6 is a schematic view for explaining a modification of theembodiment 2.

In the backlight of the embodiment 2, for example, when the light sourceof the light 4 which is incident on the light guide film 201 a is formedof a plurality of spot light sources, for example, even in a regioncloser to the side on which the light is incident, the light quantity isdecreased between two spot light sources in the side direction.Accordingly, in the backlight which uses the plurality of spot lightsources, it is preferable to arrange the through holes TH of the lightsemi-transmissive film 201 b in a state as shown in FIG. 6, for example.

FIG. 6 shows a case in which the spot light sources are arranged on tworegions L of the light guide film. With respect to a point that aplurality of rows in which a plurality of through holes TH is arrangedin parallel with a side of the light guide film 201 a on which light isincident is arranged in the transmission direction of the light, theconstitution of the embodiment 2 is similar to the constitution of theembodiment 1. Further, in a region closer to the side on which the lightis incident, spreading of light from the spot light source isinsufficient and hence, a region where the light quantity is small isformed between the spot light sources. Accordingly, by providing moreplurality of through holes TH in the region to increase the distributiondensity of the through holes TH, it is possible to further enhance thein-plane uniformity of the brightness (light quantity) of light which isincident on the display panel 1.

In this manner, in the backlight of the embodiment 2, even when the spotlight sources are used, it is possible to enhance the in-planeuniformity of the brightness (light quantity) of the light radiated onthe display panel 1.

FIG. 7 is a schematic view for explaining a variation of the embodiment2.

The embodiment 2 is configured to enhance the in-plane uniformity oflight radiated on the display panel 1 with irregular reflection of lightwhich is radiated in the direction of the display panel 1 from the lightguide film 201 a. Here, as an example of a method of reflecting lightirregularly, as shown in FIG. 4 or the like, an example which forms thethrough holes TH in the light semi-transmissive film 201 b is shown.However, instead of forming the through holes TH in the lightsemi-transmissive film 201 b, for example, as shown in FIG. 7, it ispossible to obtain the similar advantageous effect by forming a patternwhich irregularly reflects the light (hereinafter referred to as anirregular reflection pattern) RP on the interface between the lightguide film 201 a and the reflective film 201 c.

When such an irregular reflection pattern RP is formed on the interfacebetween the light guide film 201 a and the reflective film 201 c, forexample, as shown in FIG. 7, the light 4 which is incident from acertain position of the light guide film 201 a propagates through thelight guide film 201 a following a path indicated by a solid-line arrow.Here, the light reflected on the irregular reflection pattern RP of thereflective film 201 c changes the path and the incident angle to theinterface with the light semi-transmissive film 201 b is changed beforeand after the light is reflected on the irregular reflection pattern RP.Here, the incident angle of the light is decreased after the light isreflected on the irregular reflection pattern. When the light isincident at a deep angle, a portion of the light is refracted with theinterface with the light semi-transmissive film 201 b and radiated inthe direction where the display panel 1 is arranged. Accordingly, in thesame manner as the case in which the through holes TH are formed in thelight semi-transmissive film, the in-plane uniformity of the brightness(light quantity) of the light radiated to the display panel 1 isenhanced.

Further, here, the light guide film 201 a and the reflective film 201 chave the integral structure by being adhered using a transparent opticaladhesive agent, for example, and there is no gap on the interface.Accordingly, it is possible to prevent the increase of the loss of lightdue to the leaking of light from the interface between the light guidefilm 201 a and the reflective film 201 c.

Here, when the irregular reflection pattern RP is formed at theinterface between the light guide film 201 a and the reflective film 201c, the irregular reflection pattern RP may be arranged, in the samemanner as the arrangement of the through holes TH in the lightsemi-transmissive film 201 b shown in FIG. 4 or FIG. 6, in a state thatthe distribution density is higher in a region remoter from the side ofthe light guide film 201 a on which light is incident or in a regionbetween the spot light sources.

Further, although, in the embodiment 2, the explanation is made withrespect to the example in which the light semi-transmissive film 201 bis used, it is needless to say that the polarization reflective film 201d may be used in place of the light semi-transmissive film 201 b.

Further, although, in the embodiment 2, for example, as shown in FIG. 4,the through holes TH are arranged in a row, it is needless to say thatthe through holes TH may be arranged at arbitrary positions.

(Embodiment 3)

FIG. 8 is a schematic view showing the schematic constitution of abacklight of an embodiment 3 according to the present invention.Further, FIG. 9 is a cross-sectional view taken along a line B-B′ inFIG. 8.

In the embodiment 3, a constitutional example of the light radiationportion 201 which enables the in-plane uniformity of the brightness(light quantity) of the light radiated on the display panel 1 on thepremise of the constitution of the embodiment 1 and in a methoddifferent from the embodiment 2 is explained.

Here, the light radiation portion 201 of the backlight is, as shown inFIG. 8 and FIG. 9, formed in the integral structure by sandwiching thelight guide film 201 a between the light semi-transmissive film 201 band the reflective film 201 c. The thickness of the light guide film 201a is set to 0.25 mm and less. Further, the thicknesses of the lightsemi-transmissive film 201 b and the reflective film 201 c arerespectively set to 0.05 mm or less. Further, the light guide film 201a, the light semi-transmissive film 201 b and the reflective film 201 care made of the materials which are explained in the embodiment 1.Further, the light guide film 201 a, the light semi-transmissive film201 b and the reflective film 201 c are formed in the integral structurein such a manner which is explained in conjunction with the embodiment1.

Further, in the case of embodiment 3, the light semi-transmissive film201 b is provided with a pattern which blocks light on a plurality ofportions (hereinafter, referred to as a light blocking pattern) BP. Thislight blocking pattern BP is, for example, formed by printing the whiteink or the like.

Further, the light blocking patterns BP are, for example, as shown inFIG. 8, formed in such a state that a plurality of rows in which aplurality of light blocking patterns BP is arranged in parallel to aside of the light guide film 201 a on which a region L on which light isincident is formed is arranged in the transmission direction of thelight. Here, as shown in FIG. 8 it is preferable to set intervalsbetween the respective light blocking patterns BP G1, G2, G3, G4, G5,G6, G7 in a state that the remoter the interval from the side of thelight guide film 201 a on which the light is incident, the smaller thegap becomes. Further, although the number of rows of the light blockingpatterns BP is eight in an example shown in FIG. 8, it is needless tosay that the number may be other than eight.

When the light blocking patterns BP are provided to the lightsemi-transmissive film 201 b, for example, as shown in FIG. 9, the light4 which is incident from a certain position of the light guide film 201a propagates through the light guide film 201 a following a pathindicated by a solid-line arrow. Here, the light which is reflected onthe reflective film 201 c and is incident on the interface with thelight semi-transmissive film 201 b is blocked (reflected) with the lightblocking patterns BP and hence, the light is not radiated in thedirection where the display panel is arranged after propagating throughthe light transmissive film 201 b. That is, by providing the lightblocking patterns BP, it is possible to limit the light quantity of thelight radiated in the direction where the display panel 1 is arranged.Accordingly, compared to the case of the embodiment 1, the in-planeuniformity of the brightness (light quantity) of the light radiated onthe display panel 1 is enhanced.

Further, here, the light which propagates through the light guide film201 a exhibits a large light quantity in a region closer to the side onwhich the light is incident and the light quantity is graduallydecreased as the region recedes from the side on which the light isincident. Accordingly, as shown in FIG. 8, by increasing thedistribution density of the light blocking patterns BP in the regionclose to the side on which the light is incident and by decreasing thelight quantity of the light radiated in the direction where the displaypanel 1 is arranged, the in-plane uniformity of the brightness (lightquantity) of the light radiated on the display panel is furtherenhanced.

FIG. 10 is a schematic view for explaining a modification of theembodiment 3.

In the backlight of the embodiment 3, for example, when the light sourceof the light 4 which is incident on the light guide film 201 a is formedof a plurality of spot light sources, for example, even in the regioncloser to the side on which the light is incident, the light quantity isdecreased between two spot light sources in the side direction.Accordingly, in the backlight which uses the plurality of light sources,it is preferable to arrange the light blocking patterns BP in a state asshown in FIG. 10, for example.

FIG. 10 shows a case in which the spot light sources are arranged on tworegions L of the light guide film 201 a. With respect to a point that aplurality of rows in which a plurality of light blocking patterns BP isarranged in parallel to a side of the light guide film 201 a on whichthe light is incident is arranged in the propagating direction of thelight, the constitution of the embodiment 3 is similar to theconstitution of the embodiment 1. Further, in a region closer to theside on which the light is incident, spreading of light from the spotlight source is insufficient and hence, a region where the lightquantity is small is formed between the spot light sources. Accordingly,by increasing the distribution density of the light blocking pattern inthe region immediately front of the spot light source where the lightquantity is large in the region close to the side where the light isincident, it is possible to further enhance the in-plane uniformity ofthe brightness (light quantity) of light which is incident on thedisplay panel 1.

In this manner, in the backlight of the embodiment 3, even when the spotlight sources are used, it is possible to enhance the in-planeuniformity of the brightness (light quantity) of the light radiated onthe display panel.

Further, although, in the embodiment 3, the explanation is made withrespect to the example in which the light semi-transmissive film 201 bis used, it is needless to say that the polarization reflective film 201d may be used in place of the light semi-transmissive film 201 b.

Further, although, in the embodiment 3, for example, as shown in FIG. 8,the light blocking patterns BP are arranged in a row, it is needless tosay that the light blocking patterns BP may be arranged at arbitrarypositions.

(Embodiment 4)

FIG. 11 is a schematic view showing the schematic constitution of thebacklight of the embodiment 4 according to the present invention.Further, FIG. 12 is a cross-sectional view taken along a line C-C′ inFIG. 11. Further, FIG. 13 is a cross-sectional view taken along a lineD-D′ in FIG. 11. Here, FIG. 11 shows a front view of the backlight and aside view of the lower side of the backlight.

In the embodiment 4, on the premise of the constitution of the lightradiation portion 201 of the backlight which is explained in conjunctionwith the embodiment 1 to the embodiment 3, a constitutional example of abacklight including a light source of light which is incident on thelight guide film 201 a.

Here, the light radiation portion 201 of the backlight is, as shown inFIG. 11 to FIG. 13, formed in the integral structure by sandwiching thelight guide film 201 a between the light semi-transmissive film 201 band the reflective film 201 c. The thickness of the light guide film 201a is set to 0.25 mm or less. Further, the thicknesses of the lightsemi-transmissive film 201 b and the reflective film 201 c arerespectively set to 0.05 mm or less, for example. Further, the lightguide film 201 a, the light semi-transmissive film 201 b and thereflective film 201 c are respectively made of materials explained inconjunction with the embodiment 1. Further, the light guide film 201 a,the light semi-transmissive film 201 b and the reflective film 201 c areformed in the integral structure in such a manner which is explained inconjunction with the embodiment 1.

Further, here, the light radiation portion 201 may have, for example,through holes TH formed in the light semi-transmissive film 201 b at aplurality of positions in the same manner as the embodiment 2. Further,in place of the through holes TH, for example, an irregular reflectionpattern RP may be provided with the interface between the light guidefilm 201 a and the reflective film 201 c. Further, for example, in thesame manner as the embodiment 3, light blocking patterns BP may beprovided with the interface between the light semi-transmissive film 201b and the light guide film 201 a.

A light source of light 4 which is incident on the light guide film 201a is formed of a spot light source 202 such as an LED, for example. Thespot light sources 202 are mounted on a flexible circuit board 203, forexample. Here, the flexible circuit board 203 on which the spot lightsources 202 are mounted is arranged on, for example, on the lightsemi-transmissive film 201 b of the light radiation portion 201, andoutside a region where the light is radiated to a display region of thedisplay panel 1 (hereinafter referred to as a radiation region) IR.Further, the spot light sources 202 on the flexible circuit board 203use a side-view-type LED, for example, and are mounted in a state thatthe light is radiated in the film surface direction of the light guidefilm 201 a and in the direction opposite to radiation region IR.

Further, here, a reflector 204 is provided to an end portion of thelight guide film 201 a on a side on which the spot light sources 202 arearranged. The light 4 which is radiated from the spot light source 202is, as shown in FIG. 14 and FIG. 15, reflected on a reflective surface204 a of the reflector 204 and changes the direction thereof to theradiation region IR and, thereafter, is incident on the light guide film201 a. The manner in which the incident light 4 propagates through thelight guide film 201 a is the same manner as explained in conjunctionwith the embodiments 1 to 3 and hence, the detailed explanation isomitted.

Here, in the embodiment 4, the spot light source 202 such as LED is usedas the spot light source, and this LED is usually configured such thatthe spreading of radiated light 4 is small to enhance the brightness.Accordingly, out of the reflective surfaces 204 a of the reflectionplate 204, by forming the surface which faces the light radiationsurface of the spot light source 202 in an opposed manner, for example,to project to the spot light source 202 side as shown in FIG. 13, it ispossible to spread the light of the spot light source 202. Due to such aconstitution, it is possible to effectively propagate the light to aregion between two spot light sources 202.

FIG. 14A and FIG. 14B are schematic views for explaining a modificationof the embodiment 4, wherein FIG. 14A is a front view of a backlight andFIG. 14B is a side view of a lower portion of the backlight. Further,FIG. 15 is a cross-sectional view taken along a line E-E′ in FIG. 14A,and FIG. 16 is a cross-sectional view taken along a line F-F′ in FIG.14B.

The backlight of the embodiment 4 uses the spot light source 202 formedof a side-view-type LED, wherein light radiated toward the film surfaceof a light guide film 201 a from the spot light source 202 is reflectedon the reflector 204 and is incident on the light guide film 201 a.Here, for example, as shown in FIG. 13, by forming a reflection surface204 a which forms a convex curved surface on a spot-light-source-202side of the reflector 204, the light radiated from the spot light source202 can be spread. However, this embodiment is not limited to thereflective surface 204 a having the convex curved surface shown in FIG.13 and, it is possible to spread the light radiated from the spot lightsource 202 by also using a reflective surface 204 b which projectstoward the spot-light-source-202 side by combining planar surfaces shownin FIG. 14 to FIG. 16, for example.

FIG. 17 is a schematic view for explaining one advantageous effect ofthe backlight of the embodiment 4. Further, FIG. 18 is a schematic viewshowing a constitutional example of a display device which uses aconventional general backlight for comparison with the backlight of theembodiment 4.

The backlight of the embodiment 4 is integrally constituted of the lightguide film 201 a, the light semi-transmissive film 201 b and thereflective film 201 c thus reducing a thickness of the light radiationportion 201. Further, the spot light source 202 of the light which isincident on the light guide film 201 a is formed on the light guide film201 a, and is arranged outside a radiation region IR which radiates thelight to the display panel 1. Accordingly, in the display device whichuses the backlight of the embodiment 4, for example, as shown in FIG.17, it is possible to arrange the spot light source 202 and thereflector 204 in the direction toward the side surface of the displaypanel 1. Due to such a constitution, it is possible to absorb an amountof thickness corresponding to a height of the flexible printed circuitboard 203 and the height of the mounted spot light source 202 which isarranged over the light semi-transmissive film 201 b and hence, athickness Td of the structure obtained by overlapping the display panel1 and the backlight (the light radiation portion 201) to each other canbe reduced.

The conventional display device uses the light guide plate formed byinjection molding, for example, and the spot light source 202 isarranged on a side surface of the light guide plate 201 e as shown inFIG. 18. By providing such a constitution to the backlight, thethickness of the light guide plate 201 e becomes approximately 0.4 mm,for example. Accordingly, a thickness Te of the structure obtained byoverlapping the display panel 1 and the backlight (the light radiationportion 201) to each other becomes approximately 1.06 mm, for example.

On the other hand, in case of the display device which uses thebacklight of the embodiment 4, the thickness of the light radiationportion 201 of the backlight becomes 0.35 mm or less. Accordingly, thethickness Td of the structure obtained by overlapping the display panel1 and the backlight (the light radiation portion 201) to each otherbecomes approximately 0.95 mm.

In view of the above, with the use of the backlight of the embodiment 4,the display device can be made thin and light-weighted, and the in-planeuniformity of a light quantity of the radiation region IR is enhanced.

Here, in this embodiment 4, a case which uses the lightsemi-transmissive film 201 b is exemplified. However, it is needless tosay that a polarization reflective film 201 d may be used in place ofthe light semi-transmissive film 201 b.

(Embodiment 5)

FIG. 19 is a schematic view showing the schematic constitution of abacklight of an embodiment 5 according to the present invention, FIG. 20is a cross-sectional view taken along a line G-G′ in FIG. 19, and FIG.21 is a schematic view for explaining a mounting method of anincident-light adjusting member.

In the embodiment 5, on the premise of the constitution of the lightradiation portion 201 of the backlight explained in conjunction with theembodiment 1 to embodiment 3, another constitutional example of thebacklight which includes the light source of light incident on the lightguide film 201 a is explained.

Here, the light radiation portion 201 of the backlight is, as shown inFIG. 19 and FIG. 20, formed into the integral structure in which thelight guide film 201 a is sandwiched between the light semi-transmissivefilm 201 b and a reflective film 201 c. A thickness of the light guidefilm 201 a is set to 0.25 mm or less. Further, thicknesses of the lightsemi-transmissive film 201 b and the reflective film 201 c arerespectively set to 0.05 mm or less, for example. Further, the lightguide film 201 a, the light semi-transmissive film 201 b and thereflective film 201 c are respectively made of the material which hasbeen explained in conjunction with the embodiment 1, for example.Further, the light guide film 201 a, the light semi-transmissive film201 b and the reflective film 201 c are formed into the integralstructure using the method explained in conjunction with the embodiment1.

Further, in the light radiation portion 201, through holes TH may beformed in a plurality of portions of the light semi-transmissive film201 b as in the case of the embodiment 2, for example. Further, in placeof the through holes TH, an irregular reflection pattern RP may beprovided to an interface between the light guide film 201 a and thereflective film 201 c. Still further, for example, as in the case of theembodiment 3, a light blocking pattern BP may be provided to aninterface between the light semi-transmissive film 201 b and the lightguide film 201 a.

Further, a light source of light 4 which is incident on the light guidefilm 201 a may be a spot light source 202 formed of an LED, for example.The spot light source 202 may be mounted on the flexible printed circuitboard 203, for example. Here, the flexible printed circuit board 203 onwhich the spot light source 202 is mounted is arranged on a side of thelight radiation portion 201 (the light guide film 201 a) to which thereflective film 201 c is provided, for example and, at the same time,outside a radiation region IR which radiates light to a display regionof a display panel 1. Here, the spot light source 202 on the flexibleprinted circuit board 203 is formed of a top-view type LED, for example,and is mounted so as to radiate light in the direction perpendicular tothe film-surface direction of the light guide film 201 a.

Here, between the light guide film 201 a and the spot light source 202,an incident-light adjusting member 205 which forms a plurality ofprojections 205 a on a surface thereof which faces the light guide film201 a in an opposed manner is interposed. The incident-light adjustingmember 205 is made of a material equal to a material of the light guidefilm 201 a. Further, the incident-light adjusting member 205 has adistal end of the projection 205 a thereof formed in a flat surfaceshape and is brought into close contact with a film surface of the lightguide film 201 a.

The incident-light adjusting member 205 may preferably be formed of afilm having a thickness of 0.1 mm to 0.2 mm including the projections205 a, for example. Further, the projections 205 a may be formed byphotolithography, for example.

Further, distal end surfaces of the projections 205 a of theincident-light adjusting member 205 may be brought into close contactwith the light guide film 201 a by, for example, as shown in FIG. 21,applying an optical adhesive agent 206 to the distal end surfaces of theprojections 205 a and adhering the distal end surfaces of theprojections 205 a on the film surfaces of the light guide film 201 a.

Further, the projections 205 a of the incident-light adjusting member205 may be formed of columnar projections having curved bottom surfacesas shown in FIG. 19, for example. Further, the projections 205 a of theincident-light adjusting member 205 may, for example, as shown in FIG.20, have side surfaces thereof on a side opposite to the radiationregion IR formed into a convex curved shape.

Further, in the backlight shown in the embodiment 5, it is preferable toprovide a reflective sheet 207 which is overlapped to the incident-lightadjusting member 205 to a surface of the light guide film 201 a to whichthe light semi-transmissive film 201 b is provided.

FIG. 22 is a schematic view for explaining the manner of operation ofthe backlight of the embodiment 5.

The manner of operation of the backlight of the embodiment 5 isexplained in conjunction with FIG. 22. Here, FIG. 22 is an enlargedcross-sectional view of a region AR1 shown in FIG. 20.

In the backlight of the embodiment 5, a spot light source 202 such asthe LED is, as shown in FIG. 20, arranged such that the spot lightsource 202 radiates light in the direction perpendicular to the filmsurface of the light guide film 201 a. Accordingly, in such a state, alight from the spot light source 202 exhibits a small incident anglewith respect to the light guide film 201 a and hence, it is impossibleto make the incident light 4 propagate into the radiation region IR.Accordingly, between the spot light source 202 and the light guide film201 a, the incident-light adjusting member 205 having the projections205 a shown in FIG. 22 is interposed. Here, the light 4 which isradiated in the direction perpendicular to the film surface of the lightguide film 201 a is, for example, as shown in FIG. 22, reflected on theconvex curved surfaces of the projections 205 a of the incident-lightadjusting member 205 on a side opposite to the radiation region IR thuschanging an advancing path thereof and, thereafter, the light 4 isincident on the light guide film 201 a. The manner in which the incidentlight propagates through the light guide film 201 a is exactly as sameas the manner of propagation of the incident light explained inconjunction with the embodiment 1 to embodiment 3 and hence, thedetailed explanation is omitted.

Here, the convex curved surface of the projection 205 a of theincident-light adjusting member 205 adopts a shape which allows areflection angle θ of the light on the convex curved shape to satisfy afollowing formula (1).θ=i/2>(arc sin(1/n))/2  (1)

Here, in the formula (1), “i” indicates an incident angle of the lighton the interface between the light guide film 201 a and the lightsemi-transmissive film 201 b, and “n” indicates a refractive index ofthe incident-light adjusting member 205 and the light guide film 201 a.

The light which is radiated from the spot light source 202 such as theLED exhibits the largest component in the direction perpendicular to thefilm surface of the light guide film 201 a. However, by forming thelight components other than the light component in the perpendiculardirection to have the shape which satisfies the formula (1), it ispossible to allow such light components to be effectively incident onthe light guide film 201 a.

Further, for example, among the light which is radiated in the directionperpendicular to the film surface of the light guide film 201 a, thereexists light which passes through a portion different from the convexcurved shape of the projection 205 a. In this case, the light isincident perpendicular to the film surface of the light guide film 201 aand hence, the light is not reflected on the interface with the lightsemi-transmissive film 201 b whereby the light passes through the lightsemi-transmissive film 201 b. Accordingly, by providing a reflectivesheet 207 to a region on the light semi-transmissive film 201 b which isoverlapped to the incident-light adjusting member 205, the light whichpasses through the light semi-transmissive film 201 b is reflected onthe reflective sheet 207 thus allowing the incidence of the light on thelight guide film 201 a again.

FIG. 23 is a schematic view showing one example of a method for adheringthe spot light source and the incident-light adjusting member 205 in theembodiment 5. Further, FIG. 24 is a cross-sectional view taken along aline H-H′ in FIG. 23.

In the backlight of the embodiment 5, it is preferable to adhere thespot light source 202 such as the LED to the incident-light adjustingmember 205 using an annular adhesive agent 208 as shown in FIG. 23 andFIG. 24, for example. Here, the annular adhesive agent 208 may beprovided to an outermost periphery of a light radiation surface of thespot light source 202 for preventing the blocking of light from thelight emitting element (LED chip) 202 a which the spot light source 202possesses.

FIG. 25 is a schematic view showing one example of the arrangement ofthe backlight and the display panel of the embodiment 5. Further, FIG.26 is a schematic view showing another example of the arrangement of thebacklight and the display panel of the embodiment 5.

In the backlight of the embodiment 5, for example, as shown in FIG. 20,the incident-light adjusting member 205 and the spot light source 202are arranged on a surface side of the light guide film 201 a on whichthe reflective film 201 c is arranged. Here, the display panel 1 isarranged on a surface side of the light guide film 201 a to which thelight semi-transmissive film 201 b is provided. Accordingly, as shown inFIG. 25, the spot light source 202 is arranged on the back surface ofthe light radiation portion 201 of the backlight.

By adopting such an arrangement, for example, it is also possible toarrange the incident-light adjusting member 205 such that theincident-light adjusting member 205 is overlapped to the display panel 1partially or as a whole. Accordingly, a region of the display deviceoutside the display region, so-called a picture frame region can be madesmall.

Here, in the backlight of the embodiment 5, the spot light source 202and the incident-light adjusting member 205 may be, for example, asshown in FIG. 26, arranged on a surface side of the light guide film 201a to which the light semi-transmissive film 201 b is provided.

FIG. 27 is a schematic view for explaining a first variation of theembodiment 5.

In explaining the constitution of the backlight of the embodiment 5, thecase in which one spot light source 202 is arranged is exemplified asshown in FIG. 19, for example. However, the present invention is notlimited to such backlight constitution and, for example, two spot lightsources 202 may be arranged as shown in FIG. 27. Further, although notshown in the drawing, it is needless to say that three or more spotlight sources 202 may be arranged.

FIG. 28 is a schematic view for explaining a second variation of theembodiment 5.

In explaining the constitution of the backlight of the embodiment 5, forexample, as shown in FIG. 20, the case in which the reflective sheet 207which is overlapped to the incident-light adjusting member 205 isadhered to the light semi-transmissive film 201 b is exemplified.However, the present invention is not limited to the backlightconstitution and, for example, as shown in FIG. 28, a prism sheet 209may be arranged between the light semi-transmissive film 201 b and thereflective sheet 207. By arranging the prism sheet 209 in such a manner,light which is reflected on the reflective sheet 207 after passingthrough the light semi-transmissive film 201 b is allowed to be incidenton the light guide film 201 a again by setting a certain incident anglethus further enhancing the utilization efficiency of the light.

Further, although the explanation using drawings may be omitted, it isneedless to say that the arrangement of the plurality of projections 205a of the incident-light adjusting member 205 is not limited to thearrangement in a matrix array as shown in FIG. 19, for example. Withrespect to the arrangement of the projections, it may be possible toadopt a method in which a plurality of projections 205 a are arranged oncurved lines which project in the direction toward the radiation regionIR such as concentric circumferences about a certain point, for example.

(Embodiment 6)

FIG. 29 is a schematic view showing the schematic constitution of abacklight of an embodiment 6 according to the present invention.Further, FIG. 30 is a cross-sectional view taken along a line J-J′ inFIG. 29.

The backlight of the embodiment 6 is a backlight of another modificationof the embodiment 5, wherein the constitution of the light source 202and the vicinity of the light source 202 is equal to the correspondingconstitution of the backlight of the embodiment 5. A point which makesthis embodiment 6 different from 5 lies in the constitution of theradiation region IR of the light guide film 201 a. In the backlight ofthis embodiment 6, for example, as shown in FIG. 29 and FIG. 30, to afilm surface of a light guide film 201 a, a light semi-transmissivemember 201 b or a polarization reflective film 201 d, and a reflectivefilm 201 c are not adhered. In place of such a constitution, aradiation-light adjusting member 201 f is provided to one film surfaceof the light guide film 201 a, that is, the surface of the light guidefilm 201 a which faces the display panel 1 in an opposed manner. Theradiation-light adjusting member 201 f is a member which adjusts aradiation angle of the light which is radiated from the film surface ofthe light guide film 201 a and is radiated to the display panel 1.

Further, the radiation-light adjusting member 201 f has substantiallythe same constitution as the incident-light adjusting member 205, forexample, wherein the radiation-light adjusting member 201 f has one, twoor more projections on a surface thereof which faces the light guidefilm 201 a in an opposed manner, and distal-end surfaces of theprojections are brought into contact with a film surface of the lightguide film 201 a. Here, although the projections are arranged only in aregion close to the light source 202, in an actual arrangement, theprojections similar to the projections shown in FIG. 29 and FIG. 30 arearranged over the whole region of the radiation-light adjusting member201 f. Here, the radiation-light adjusting member 201 f may preferablybe formed of a film having a thickness of 0.05 mm including theprojections, for example. Further, the projections may be formed byphotolithography, for example.

Further, distal end surfaces of the projections of the radiation-lightadjusting member 201 f may be brought into close contact with the lightguide film 201 a by, for example, applying an optical adhesive agent tothe distal end surfaces of the projections and adhering the distal endsurfaces of the projections on the film surfaces of the light guide film201 a.

Further, the projections of the radiation-light adjusting member 201 fmay be formed of columnar projections having curved bottom surfaces asshown in FIG. 29, for example. Further, the projections of theradiation-light adjusting member 201 f may, for example, as shown inFIG. 30, have side surfaces thereof on a side opposite to the lightsource 202 formed into a convex curved shape.

Here, also in the backlight of the embodiment 6, a thickness of thelight guide film 201 a is set to 0.25 mm or less. Further, the lightguide film 201 a may be made of polycarbonate (PC) having a refractiveindex of 1.59.

The backlight of the embodiment 6 does not use the lightsemi-transmissive film 201 b or the polarization reflective film 201 dand the reflective member 201 c. However, the refractive index of thelight guide film 201 a is larger than the refractive index of air andhence, the light 4 which is incident on the light guide film 201 a afterpassing through the incident-light adjusting member 205 repeats thetotal reflection on the film surface, that is, on an interface betweenthe light guide film 201 a and air and propagates in the inside of thelight guide film 201 a.

Here, at portions where the projections of the radiation-light adjustingmember 201 f and the light guide film 201 a are brought into contactwith each other, the refractive index is substantially equal and hence,no total reflection occurs whereby the light 4 advances to the inside ofthe projections of the radiation-light adjusting member 201 f directly.Then, the light 4 which enters the inside of the projections arereflected on the interfaces between the side surfaces of the projectionsand air and, thereafter, is radiated in the direction toward the displaypanel 1.

In this manner, according to the backlight of the embodiment 6, with theuse of the radiation-light adjusting member 201 f in place of the lightsemi-transmissive film 201 b or the polarization reflective film 201 dand the reflective film 201 c, it is possible to obtain the advantageouseffects substantially equal to the advantageous effects obtained by thebacklight of the embodiment 5. Accordingly, it is possible to decreasekinds of sheets (films) which are adhered to the light guide film 201 aand hence, the light guide film 201 a can reduce the thickness thereofthus realizing the backlight at a low cost.

Although the present invention has been specifically explained inconjunction with the embodiments, it is needless to say that the presentinvention is not limited to the above-mentioned embodiments and variousmodifications are conceivable without departing from the gist of thepresent invention.

The backlights which have been explained in conjunction with respectiveembodiments are thin and light-weighted and, at the same time, exhibithigh brightness uniformity of the radiation surface. Accordingly, theconstitutions of the backlights which are exemplified in the respectiveembodiments may not be limited to the light source of the display devicesuch as the liquid crystal display device and may be applicable to aplanar light source device (unit) such as illumination equipment, forexample.

What is claimed is:
 1. A display device comprising: a display panel; alight guide member having a first surface and a second surface which isopposed to the first surface; a light source formed of at least one LED;and a light adjusting member arranged between the light source and thefirst surface of the light guide member, wherein the light adjustingmember has at least one projection on a surface side which faces thefirst surface of the light guide member, and distal end surfaces of theprojections are contact with the first surface of the light guidemember, and wherein the first surface of the light guide member isfacing toward the display panel.
 2. A display device according to claim1, wherein the light adjusting member has a plurality of projections ona surface side which face the first surface of the light guide member.3. A display device according to claim 1, wherein a reflective member isprovided to the second surface of the light guide member opposite to thefirst surface.
 4. A display device according to claim 3, wherein aprojection of the incident-light adjusting member is a columnarprojection having a curved bottom surface.
 5. A display device accordingto claim 1, wherein thickness of the light guide member is 0.25 mm orless.
 6. A display device according to claim 3, wherein a reflectivemember is provided to the second surface of the light guide memberopposite to the first surface.
 7. A display device according to claim 6,wherein a projection of the incident-light adjusting member is acolumnar projection having a curved bottom surface.
 8. A display deviceaccording to claim 1, wherein the second surface of the light guidemember is facing toward the display panel.
 9. A display device accordingto claim 8, wherein a reflective member is provided to the first surfaceof the light guide member opposite to the second surface.
 10. A displaydevice according to claim 9, wherein a projection of the incident-lightadjusting member is a columnar projection having a curved bottomsurface.
 11. A display device according to claim 8, wherein thickness ofthe light guide member is 0.25 mm or less.
 12. A display deviceaccording to claim 11, wherein a reflective member is provided to thefirst surface of the light guide member opposite to the second surface.13. A display device according to claim 12, wherein a projection of theincident-light adjusting member is a columnar projection having a curvedbottom surface.